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CU-Boulder instruments to help unlock mystery of Earth's radiation belts

By Laura Snider Camera Staff Writer

Posted:
08/23/2012 07:08:06 PM MDT

Updated:
08/23/2012 07:10:02 PM MDT

When the United States launched its first-ever satellite, Explorer 1, in 1958, a Geiger counter onboard revealed the existence of two doughnut-shaped belts of radiation that wrap around the Earth.

More than a half-century later, NASA has built a pair of brawny space probes -- which carry two instruments worked on by scientists at the University of Colorado -- that are about to be on their way, assuming Friday morning's launch goes smoothly, to get a better look at the high-radiation zones, known as the Van Allen Belts.

NASA's octagonal Radiation Belt Storm Probes are headed into an elliptical orbit around Earth that will send both spacecraft through the inner and outer belts -- which are thick with high-energy particles that can be damaging to spacecraft and, potentially, to future astronauts passing through -- as they fly around the Earth taking measurements.

"The RBSP spacecraft has to hang out in the radiation belt, which most other spacecraft try to avoid," said David Malaspina, a scientist at CU's Laboratory for Atmospheric and Space Physics who worked on one of the instruments onboard. "RBSP is built kind of like a space tank."

High-energy particles can damage electronics when they barrage a spacecraft because the energy in the particles can transfer to the electronics, essentially overwhelming them.

"Basically, you're knocking around a bunch of electrons inside your electronics," Malaspina said. "You're putting too much energy into certain junctions, and that's what actually does the damage."

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CU researchers worked on two instruments onboard the probes, both of which were "hardened" to withstand the intense conditions in the Van Allen Belts, named after James Van Allen, who led the development of Explorer 1.

Malaspina and colleague Robert Ergun were two of the people who worked on the Digital Fields Board, the "brains" of the Electric Field and Waves Suite. The Digital Fields Board is a type of controller that is a LASP specialty.

"What LASP is well-known for is really building these controllers that take measurements, package them up, do a lot of onboard analysis and pre-selection, and get them ready for the onboard transmission down to the ground," Ergun said.

Processing some of the data in space, instead of on the ground, allows researchers to send a smaller quantity of data back to Earth.

"Most people don't realize that satellite communication is not very fast," Ergun said. "Our allocation is something like 8 kilobits per second, which is less than your average phone modem used to be."

LASP researchers also developed the Relativistic Electron Proton Telescope, which is designed to measure the highest-energy particles found in the radiation belts. The telescope will measure the energy of the particles as they hit a silicon detector. Scientists hope the data collected by all the instruments on the probe will help them better understand the origin of the belts and how they change as space weather changes.

For example, particularly intense solar flares that hurl plasma toward the Earth, known as coronal mass ejections, can excite the belts, causing them to expand, possibly into the zone around the Earth where communications, weather and GPS satellites hang out.

A better understanding of how the belts react to solar storms could help operators better protect those satellites. And in the future, if astronauts head to the moon or Mars or any other destination away from Earth, a better understanding of the radiation belts that circle the Earth will help engineers design a spacecraft that can keep the astronauts safe as they pass through.

"Because the Van Allen radiation belts were the first discovery of the space age, the origin and fate of these relativistic, high-energy electrons is perhaps the longest standing puzzle in space research," said LASP Director Daniel Baker, who led the development of the Relativistic Electron Proton Telescope, in a news release.

The storm probes were scheduled to launch at 2:07 a.m. Friday from Cape Canaveral, Fla.

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